Self-piercing nuts are known in the art, wherein each nut itself punches a hole in a metal sheet or panel so that the rim of this hole is simultaneously caulked and pressed into the nut's side groove. Also known in the art is an apparatus constructed to attach each nut in this manner particularly to the inner wall surface of a metal. This nut will be used to engage with a screw driven inwards from the outside of the pipe, and such a prior art is disclosed in the Patent Document 1.
The apparatus proposed in this document was of a manually-operating type and has gotten out of date year by year and up to now, thus failing to be used widely.
Patent Document 1: Japanese Patent Publication No. 53-16394